Acoustic wave devices using acoustic waves are small and light, can obtain high attenuation against signals outside a given frequency band, and thus are used as a filter for wireless devices such as mobile phone terminals. The acoustic wave device includes an electrode such as an IDT (Interdigital Transducer) formed on a piezoelectric substrate.
There has been known irradiating a piezoelectric substrate with a laser beam to separate acoustic wave chips formed on the piezoelectric substrate into individual ones. For example, there is disclosed a laser processing equipment that irradiates a wafer with a laser beam in Japanese Patent Application Publication No. 2008-100258. There is disclosed irradiating a piezoelectric substrate with a laser beam to dice the piezoelectric substrate wafer in Japanese Patent Application Publication No. 2001-345658. There is disclosed a method of bonding a semiconductor wafer to a tape and then dicing the semiconductor wafer in Japanese Patent Application Publication No. 2010-182901.
When a piezoelectric substrate is irradiated with a laser beam, debris is easily formed if a metal layer formed on the piezoelectric substrate is irradiated with the laser beam. Scattering of conductive debris on electrodes formed on the piezoelectric substrate causes short circuit between the electrodes, or causes a change in characteristics of the acoustic wave device.